Vitamin C increases 5-hydroxymethylcytosine level and inhibits the growth of bladder cancer.

5-Hydroxymethylcytosine (5hmC) is converted from 5-methylcytosine (5mC) by a group of enzymes termed ten-eleven translocation (TET) family dioxygenases. The loss of 5hmC has been identified as a hallmark of most types of cancer and is related to tumorigenesis and progression. However, the role of 5hmC in bladder cancer is seldom investigated. Vitamin C was recently reported to induce the generation of 5hmC by acting as a cofactor for TET dioxygenases. In this study, we explored the role of 5hmC in bladder cancer and the therapeutic efficacy of vitamin C in increasing the 5hmC pattern. 5hmC was decreased in bladder cancer samples and was related to patient overall survival. Genome-wide mapping of 5hmC in tumor tissues and vitamin C-treated bladder cancer cells revealed that 5hmC loss was enriched in cancer-related genes and that vitamin C treatment increased 5hmC levels correspondingly. Vitamin C treatment shifted the transcriptome and inhibited the malignant phenotypes associated with bladder cancer cells in both in vitro cell lines and in vivo xenografts. This study provided mechanistic insights regarding the 5hmC loss in bladder cancer and a rationale for exploring the therapeutic use of vitamin C as a potential epigenetic treatment for bladder cancer.